Measurement of diffuse photon-pairs density wave in a multiple-scattering medium

Abstract

As a continuation of the previously developed theory of a diffuse photon-pairs density wave (DPPDW) [Appl. Opt.44, 1416-1425 (2005)APOPAI0003-693510.1364/AO.44.001416], this research experimentally studies and verifies the DPPDW theory in a heterogeneous multiple-scattering medium. The DPPDW is generated by collecting the scattered linear polarized photon pairs (LPPPs) in the multiple-scattering medium. Theoretically, the common-path propagation of LPPPs not only provides common phase noise rejection mode but also performs coherence technique via heterodyne detection. In addition, the polarization gating and spatial coherence gating of LPPPs would suppress the severe scattered photon in the multiple-scattering medium. In the experiment, the amplitude and phase wavefronts of DPPDWs, which are distorted by a small object embedded in a homogeneous multiple-scattering medium, are measured in one dimension or two dimensions by scanning the source detector pair. The measured distortion of DPPDW wavefronts are detected precisely and are consistent with the theoretical calculation of DPPDW. It implies an improvement on the detection sensitivity of a small object compared with the conventional diffuse photon density wave (DPDW).

Glucose detection in a highly scattering medium with diffuse photon-pair density wave

“…2(c), a TFL with higher beat frequency and larger output power is suggested in this setup for better performance according to our previous discussion using DPPDW. 10,11 Generally, the absorption e®ect can be ignored in most glucose detection methods via NIR light. 5,6,9 However, for high absorption coe±cient of MSM such as human tissue, the absorption e®ect cannot be ignored.…”

“…16 As a result, moderately scattering PPP is selected via spatial coherence gating and polarization gating. 10,11 The real part of the wavenumber k 2r of DPPDW is given by…”

“…The glucose concentration can be measured in terms of reduced scattering coe±cients 0 2s and absorption coe±-cients 2a that were measured by photon pairs. 10,11 In contrast to DPDW, the DPPDW in MSM uses lower amplitude modulation frequency (20 MHz) via heterodyne interference and highly correlated polarized photon pairs (PPPs). A two-frequency He-Ne laser produces DPPDW in turbid media, and the amplitude and phase of the heterodyne signal are detected simultaneously.…”

Surface effect measurement of a small scattering object in highly scattering medium by use of diffuse photon-pairs density wave

“…The DPPDW method depends on the heterodyne interference of LPPP in scattering media, where the path dependent phase and the common background phase noise are reduced by the common-path configuration of LPPP. In addition, the properties of the polarization gating and spatial coherence gating of DPPDW can reduce the noise from the severe scattering photon [8,10]. These reveal a higher SNR and detection sensitivity.…”

“…Therefore, imaging by NIR not only suffers poor spatial resolution but also makes the inverse problem noise-sensitive [4]. In order to improve the spatial resolution, more information on image recovery such as the boundaries of the imaging object has to be involved [5][6][7][8]. Thus, the signal induced by the boundaries of imaging object in a highly scattering medium is the focus of this letter.…”